Optical instrument for measuring the distance between the eyes.



Nu.l 688,987. Patented Dec. I7, |90I.

E. nmz. OPTICAL INSTRUMENT FOBQMEASUHING THE DISTANCE BETWEEN THE EYES.

'('ppxmtion med .my 25, 1901., (No Nudel.)

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NITED STATES EMIL DNITZ, OF JENA, GERMANY, ASSIGNOR TO THE FIRM OARL ZEISS,

OF JENA, GERMANY.

OPTICAL INSTRUMENT FOR MEASURING THE DISTANCE BETWEEN THE EYES.

sP'ncIFIcATIoN forming part of Letters Patent No. 688,987, dated :December 17, 1901.

Application filed July Z5, 1901. Serial No. 69,701. (No model.)

To rtZZ whom t may concern.-

Be it known that I, EMIL DNITZ, engineer, a subject of the Duke of Anhalt, residing at Carl Zeiss strasse, Jena, in the Grand Duchy of SaXe-TVeimar, German Empire, have invented a new and useful Optical Instrument for Measuring the Distance Between the Eyes, of which the following is a specification.

rPhe present invention consists in an optical instrument by means of which an optician may more exactly determine the distance between the pupils of his clients eyes than in any Way hitherto known. In this instrument two mirrors and a scale are combined. One mirror reproduces the scale in proximity of the patients pupils and in the plane of these pupils, so that the observer is prevented from any parallactic error when using both eyes in reading the position of the pupils relatively to the scale-image. The other mirror enables the patient to successively direct one and the other eye straight ahead by fixing both his eyes upon the image at iirst of one and then of the other eye, while the observer reads at the scale-image the position of the one and the other eye, respectively.

In the annexed drawings, Figure lis a diagram of a combination of a scale and two mirrors which is arranged according to the invention. Fig. 2 is a sectional elevation ot' an instrument constructed according to the in- Vention. Fig. 3 is a plan View of the same instrument, showing the first stage of the operation. Fig. et is another plan View showing the second stage of the operation.

In the diagram shown in Fig. l, a represen ts the eyes the distance between which is to be measured, and b represents the eyes of the observer. The eyes ct look into the mirror c and perceive therein one or the other of their images a0. The eyes b look upon one or the other of the eyes ct and into the mirror d and perceive therein an image e0 of the scale e at the same distance as the pupils ot the eyes ct. It will be understood that the position of the scale-image e0 may be approached to the actual position 'of the eye ct by moving either the mirror CZ or the scale e, or both of them.

A modified arrangement of mirror d and scale e has been employed in the instrument shown in Figs. 2 to 4. In this construction the mirror CZ is above and the scale e below the plane connecting the eyes ct and ZJ; but it will be understood that mirror and scale might also be arranged both above as well as both below the said plane.

The frame of the instru ment consists of two longitudinal rods ff and two transversal bars g and 7i. The mirror cl is fastened on a sleeve t, by means of which it maybe carried along on one of the rods f for the purpose of approaching it to myopie eyes ct and removing it from hypermetropic eyes a. The transversal bar g rests on the nose of the observer by means of its yoke 7c, Fig. 2, which is deep enough to allow the eyes l? of the observer to look above the lateral parts of bar g. The transversal bar h carries asmall nose-yoke Z, Fig. 2, for the examinee. On a transversal rod m, secured in brackets n of the longitudinal rodsf, the scale e' is loosely mounted, so that it may be rotated, as well as moved endwise, for which both purposes a diskshaped handle o is provided.

The operation is as follows: The observer puts the instrument byits yoke Zon ythe nose of the examinee so as to see the pupils of the examines immediately below the mirror d and causes his own nose to enter the yoke 7.a. Then while his left hand is holding the instrument by its left rod f, he turns the scale, seizing hold of its disk o until thelower terminations of the graduation-lines of the scaleimage, as seen by him in the mirror d', enter the pupilar plane of the eyes d. Thereupon he causes the examinee to have both eyes d1 and d, fixed upon the center of the image GL01 of his left eye al, Fig. 3, so as to give the eye al the same direction as when both eyes look ahead into the distance. The observer himself directing both eyes b1 and b1. to the center of the pupil of the eye al, as shown in Fig. 3, moves the scale c endwise for the purpose of bringing the zero-line of the scale-irnage exactly above the said center. This done, he causes the examinee now to direct the eyes upon the center of the image ttor, Fig. 4, of his right eye ar and reads on the scale-image the position of the pupilar center of eye c... The

value observed is the correct distance between the eyes of the examinee looking ahead into the dist-ance.

IOO

What I claim as my invention, and desire to secure by Letters Patent, is-

l. The combination, with ascale longitudinally arranged on a horizontal bar, of two narrow mirrors extending parallelly to the scalebar and so located relatively to the scale, that the iirst mirror produces animage ofthe scale, that the second mirror is situated in a direction from the iirst mirror contrary to that of the image, and that an eye in proximity of this image may seeitself in the second mirror, and a frame connecting the scale-bar and both mirrors, essentially as described.

2. In an instrument for measuring the distance between both eyes the combination with a scale longitudinally arranged on ahorizontal bar of two narrow mirrors extending parallelly to the scale-bar and so located relatively to the scale, that the rst mirror 'produces an image of the scale and that the sec'- ond mirror is situated in a direction from the first mirror contrary to that ofthe image and enables an eye which is in proximity of the EMIL DNITZ.

Witnesses:

PAUL KRGER, JACOB HECKEL. n 

